A Data Mining Approach for Detecting Collusion in Unproctored Online Exams


J. Langerbein, T. Massing, J. Klenke, N. Reckmann, M. Striewe,
M. Goedicke, C. Hanck


University of Duisburg-Essen; Germany

Setting

  • Data from the Descriptive Statistics course at the U Duisburg-Essen, Germany
  • Exams consist of arithmetical problems, programming tasks in R, and a short essay task
  • Both exams are conducted digitally with the e-assessment system JACK
    • Each student receives different randomized numerical values across all tasks
    • Event logs capture students’ activities, time stamps, and points during the exams for every subtask
Comparison Test
Year 18/19 20/21
N 109 151
Style proctocred unprocotored
Total points 60 60
Sub tasks 19 17
Duration 70 70
  • The test group took the unproctored exam at home during the pandemic
    • The comparison group took a proctored exam in the facilities of the university
  • Data cleaning is conducted, removing students with minimal participation or achievement and students with internet problems

Aim of the Paper

Categorize students with a hierarchical clustering algorithm on event logs and strengthen the analysis with a proctored comparison group

Methodology

  • The study utilized an agglomerative (bottom-up) hierarchical clustering algorithm that can be described by following equation:

\[D(s_i, s_{i'}, v_i, v_{i'}) = \frac{1}{h} \sum_{j=1}^h (w_j^P \cdot d_j^P (s_{ij}, s_{i'j}) + w_j^L \cdot d_j^L (v_{ij}, v_{i'j}))\]

      • \(D(s_i, s_{i'}, v_i, v_{i'})\) the global pairwise dissimilarity
      • \(d_j^P(s_{ij}, s_{i'j})\) points dissimilarity for each task \(j\)
      • \(d_j^L(v_{ij}, v_{i'j})\) students event patterns dissimilarity for each task \(j\)
      • \(\sum_{j=1}^h w_j^P + w_j^L =1\) weight of each attribute \(h\)
  • We reduce the weights for
    • R-tasks, as these tasks have more noise
    • Essay questions, as the comparison on that kind of task are limited
    • Points achieved
  • Dissimilarities in points achieved for each task \(j\)

\[d_j^P(s_{ij}, s_{i'j}) = | s_{ij} - s_{i'j} |\]

      • \(s_{ij}\) denotes the points achieved by student \(i\) in the \(j\)-th subtask
      • Manhatten metric
  • Dissimilarities in the students event patterns (time of submission) for each task \(j\)

\[d_j^L(v_{ij}, v_{i'j}) = \sum_{m=1}^{K=70} | v_{ijm} - v_{i'jm} |\]

      • \(d_j^L(v_{ij}, v_{i'j})\) students event patterns dissimilarity for each task \(j\)
      • Examination is divided into \(m = 1, ... , 70\) time intervals
      • \(v_{ijm}\) denotes the number of answers of student \(i\) for task \(j\) in the \(m\)-th interval

Empirical Results

Dendogram produced by average linkage clustering of the unproctored test group (2020/21). <strong> A-F </strong> mark the clusters with the lowest dissimilarity.

Figure 1: Dendogram produced by average linkage clustering of the unproctored test group (2020/21). A-F mark the clusters with the lowest dissimilarity.

  • Figure 1 shows the dendrogram of the test group
    • Overall a lower level of dissimilarity compared to the comparison group
    • Six clusters (A-F) standing out noticeably from the rest of the cohort
Eevent logs and achieved points of the cluster <strong>B</strong> from the test group (2020/21). Above the scatter plot, a bar chart is added to compare the points per subtask.

Figure 2: Eevent logs and achieved points of the cluster B from the test group (2020/21). Above the scatter plot, a bar chart is added to compare the points per subtask.

  • Figure 2 illustrates the individual comparison of achieved points and event logs of the student cluster with the highest similarity
    • Similar time path and same points for each task
Comparison of the  normalised distance measures.

Figure 3: Comparison of the normalised distance measures.

  • Figure 3 compares the normalized distributions of the dissimilarity measures between the comparison and test groups

Discussion

  • Three notable clusters (A, B, and E) consisting of two students each
  • Collusion in larger groups are not found
  • Findings the same with other linkage methods and parameter specifications as weightings
  • The approach provides a basis for the examination of clusters based on comparison with a reference group